Delay timer with selector switch



Feb. 18, 1969 ESHLEMAN ETAL 3,428,763

DELAY TIMER WITH SELECTOR SWITCH Original Filed April 5, 1965 sheet 5 FIG. l- LOAD 40 I L ENERGY I CELL E ZERO INDiCATOR INVENTORS. RALPH e. ESHLEMAN JAMES w. FARMER ATTORNEYS. I

' Feb. 18, 1969 R. a. ESHLEMAN ET AL DELAY TIMER WITH SELECTOR SWITCH Sheetiofs Original Filed April 5, 1965 DIRECTION t OF FLIGHT FIG. 2

INVENTO RALPH G. ESHLEMAN JAMES W. FARMER Zia 4% ATTORNEYS.

R. G ESHLEMAN ET AL DELAY TIMER WITH SELECTOR SWITCH Feb. 18, 1909 Sheet Original Filed April 5, 1965 FIG. 5

FIG. 4

INVENTOR5. RALPH G. ESHLEMAN JAMES W. FARMER i543 v/J53 ATTORNEY-Q United States Patent Office 3,428,763 Patented Feb. 18, 1969 3,428,763 DELAY TIMER WITH SELECTOR SWITCH Ralph G. Eshleman and James W. Farmer, Lancaster, Pa., assignors to Hamilton Watch Company, Lancaster, Pa., a corporation of Pennsylvania Continuation of application Ser. No. 445,550, Apr. 5, 1965. This application May 29, 1967, Ser. No. 642,243 US. Cl. 20033 12 Claims Int. Cl. H01h 43/10 ABSTRACT OF THE DISCLOSURE Disclosed is a sequential timing switch particularly suited for igniting rocket motors. A spring driven clock mechanism drives an escapement controlled wiper arm over a series of contacts to complete one or more load circuits after a predetermined time. Important features include an arrangement for accurately zeroing the switch, a solenoid brake for automatically stopping the switch at its zero setting, a short delay clock for releasing the brake, and utilization of a set-back mass for starting the switch in response to acceleration forces.

The present application is a continuation of copending application Ser. No. 445,550, filed Apr. 5, 1965, now abandoned.

This invention relates to a timing device and more particulary to a mechanical timer or delay unit particularly suited for use in igniting rocket motors. The device is completely mechanical in operation and incorporates a novel zero setting arrangement which eliminates the need for clutches, brakes, or the other similar mechanical devices of previous timers. It provides an increase in timing accuracy of approximately an order of magnitude over currently used delay pyrotechnic igniters for rocket motors.

In firing a rocket, missile or other type of projectile it is frequently desirable that some additional function or operation be performed at a certain given time subsequent to lift-01f or firing of the missile. For example, artillery shells, rockets, and other military projectiles are frequently provided with timing devices which arm the projectile only after it has traveled a safe distance from the point of initiation. In devices of the military projectile type, the arming delay may be measurable in terms of only fractions of a second so that the accuracy of the timing device is not too important. Consequently these devices are more often designed with an eye to reliability and safety rather than extreme timing accuracy.

On the other hand, with the advent of multi-stage rockets and missiles, it frequently occurs that the desired function, such as ignition of a second or subsequent stage rocket motor, must be performed quite some time after a lift-off, i.e., as much as 30 seconds or more subsequent to the firing of the missile. In situations of this type the accuracy of the time delay becomes quite important since the firing accuracy and ultimate path of the missile depends to a large extent upon accurately timed ignition of the rocket engines. Variations of only a fraction of a second can seriously affect not only the final velocity but also the ultimate path of travel of the missile.

The present invention is directed to an intermediate type igniting or timing device standing between the cheap, simple, and very inaccurate powder train delay used in sounding rockets and the like and the complex units used in high-yield military missiles. The subject device realizes about 95% of the accuracy of the sophisticated timers With-a cost comparable with that of the pyrotechnic delay.

The delay systems currently in use for firing sounding rocket secondary stage engines are based upon a pyrotechnic delay having an accuracy of only approximately i20%. On the other hand, the mechanical delay timer of the present invention is capable of accuracies of 12% and better, which represents at least an order of magnitude improvement over present practices.

The entire timing system of the present invention is of relatively small size and light weight particularly suited for space applications. It includes: first a safety and arming device incorporating a spring-mass accelerometer and a short delay clock; second -a long delay mechanical clock based upon a conventional Junghans fuze escapement; and third a selector switch driven by the long delay clock. The unit is adjustable to provide any one of a variety of selectable delay times and is susceptible of rapid and simple adjustment even in the field.

As is well known, the accuracy of any mechanical timing device depends not only upon its running accuracy but also the accuracy with which it is initially set or zeroed. Important features of the present invention include a simplified arrangement for accurately zeroing the mechanical timer of this invention, which zeroing operation can be performed either at the factory, or in the field, or both. In addition, simplified and improved auxiliary apparatus is provided for automatically zeroing the timer in situations where greater accuracy is desired.

It is therefore one object of the present invention to provide a novel improved timer.

Another object of the present invention is to provide a timer particularly suited for use in igniting rocket motors.

Another object of the present invention is to provide a novel and improved mechanical rocket engine delay igniter.

Another object of the present invention is to provide a timer having improved means for zeroing the timer.

Another object of the present invention is to provide an accurate, relatively inexpensive delay timer having light weight and small size, particularly suited for areospace applications.

Another object of the present invention is to provide a spring driven mechanical timer particularly suited for determining the delay in firing of a second or subsequent stage in a multi-stage rocket. The device of the present invention includes a novel rotary selector switch having a wiper arm adapted to engage in sequence a plurality of output terminals, which terminals provide a selectable delay for the system. Also provided is a zero setting terminal adapted to be engaged by the wiper arm which zero terminal cooperates with a common terminal of the selector switch to accurately indicate a zero setting for the switch. Once the selector switch is seen to be in the zero position it may be manually stopped by the operator. Alternatively a novel solenoid stopping mechanism is provided in the present invention for automatically and accurately stopping the timer at the zero position. Initiation of the timing sequence commences when the unit is subjected to acceleration forces at lift-off.

These and further objects and advantatges of the invention will be more apparent upon reference to the FIGURE 4 is a cross-section through the timing wafer taken along line 4--4 of FIGURE 2 is not shown.

FIGURE 5 is a diagrammatic view showing the automatic zero setting stopping mechanism of the timer of this invention, and

FIGURE 6 is a diagrammatic plan view further illusitrating the stopping and starting mechanism of the timer.

Referring to the drawings, FIGURE 1 shows the selector switch of the present invention generally indicated at 10 comprising an output shaft 12 which carries for rotation therewith a rotor 14 and a wiper arm or shorting clip 16. As more fully described below, shaft 12 is driven from a spring powered mechanical timer or clockwork mechanism hereinafter referred to as the long delay mechanical clock.

Shorting clip 16 is adapted to sequentially engage a plurality of delay contacts 18 labelled D through D with each of the delay contacts suitably coupled to a corresponding output terminal 20. Also positioned in the path of movement of the shorting arm or spring clip 16 is a zero contact 22 coupled to terminal 24. In addition shorting clip 16 is continuously coupled through the rotor 14 to a common contact 26 and hence to a switch terminal 28.

Each of the delay contacts D through D is spaced circumferentially around rotor 14 but they are not necessarily equidistant from each other. Since the rotor is driven by the timing mechanism at a substantially constant angular velocity, the angular distance between each of the delay contacts from the zero contact 22 determines a particular delay which may be selected by the operator when the unit is wired up. This desired delay is selected by the technician when he wires in the next component and in the embodiment illustrated delay intervals of, for example, 1-0, l2, l4, 15, 16, 17, 18, 19, 20, 21, 22, 24, 2.6, 2.8 and 30 seconds or higher may be chosen as desired depending upon the number and the spacing of the delay contacts. FIGURE 1 illustrates delay contact D as coupled by way of an output lead 30 to a load 32. In the preferred embodiment this load constitutes at an igniter for a rocket motor or engine such that when an electrical circuit is completed through it the load unit 32 acts to ignite or fire the motor. The other terminal of the load 32 is returned by way of lead 34, terminal 36 and lead 38 to a power source 40 in the form of a batter or energy cell. Thus, when the shorting clip 16 rotates from the zero contact 22 to delay contact D, the circuit from energy cell 40 is completed to load 32 by way of lead 42, terminal 28, contact 26, rotor 14, shorting clip 16, contact D lead 30 and back through the load 32 to the other side of the energy cell.

In order to accurately zero the spring driven switch 10, the unit is provided with couplings 44 and 46 for attaching to the unit zero indicator 48 and battery 50 by way of leads '52 and 54. In operation of the switch 10 of FIGURE 1, the timer is first run to drive rotor 14 until the shorting clip 16 engages the zero contact 22. At this time the circuit is completed through zero indicator 48 to indicate that the switch and hence the clockwork mechanism driving it is zeroed. When this indication is received the operator either at the factory or in the field as the case may be may manually stop the clockwork drive so that the unit is accurately zeroed and ready for energization at the lift-off of the rocket. The quick disconnect couplings 44 and 46 make is possible to quickly connect and disconnect the zero indicator 48 and its power supply 50 to and from the switch.

FIGURE 2 shows the overall timer unit generally indicated at 60 as incorporated in a missile and includes the selector switch 10 of FIGURE 1, the energy cell or battery 40 and the igniter load 32. Also indicated as coupled to the switch by dash lines 62 and 64 are the zero indicator 48 illustrated in the form of an incandescent light in FIGURE 2 and its battery 50. The dash line showing is to indicate that the zero indicator is coupled to the unit only to zero the switch and its timer, either in the factory or in the field, and is later disconnected and removed from the unit before the missile is actually fired.

In FIGURE 2 the rotor engages delay contacts on an annular printed circuit board or wafer of suitable electrical insulating material upon which are deposited the conductive leads or contacts D D etc. Which are of electrically conductive copper and which may be deposited by any of the conventional printed circuit techniques including etching, printing, and the like. Any number of leads may be provided as desired and some thirteen delay leads are illustrated in FIGURE 2. As before, the output is taken from the terminal of delay lead D by way of lead 66 to the igniter load 32. Lead 68 from the other side of the load returns the load directly to one side of the energy cell or battery 40. The other side f the energy cell is connected by lead 70 to the common terminal 28. The underside of the timing wafer 15 is illustrated in FIGURE 3 as having on its bottom surface a circular common conductive lead 72 of electrically conductive copper, which lead is connected to a conductive eyelet 74 passing completely through the printed circuit board so that the opposite end of the eyelet in FIG- URE 3 forms the common terminal 28 in FIGURE 2. Similar conductive eyelets passing completely through the wafer 14 and spaced radially outward from the common lead 72 form the delay terminals D D etc. and the zero terminal 22 (D As illustrated in FIGURES 2 and 3, timing wafer 15 is provided with three equally spaced apertures 76, 78 and 80 by means of which the wafer 15 is secured to a top plate 82 rotatably receiving the output shaft 12 of the mechanical clock or long delay timer 84. Screws (not shown) pass through the apertures 76, 78 and 80 of the wafer and are threadedly received in the internally threaded posts 86, 88 and 90 carried by the top plate 82. The shaft 12 is indicated as rotatable in the clockwise direction in FIGURE 2 by the arrow 92.

Received over the end of output shaft 12 for rotation therewith is rotor 14 in the form of an arbor 94 made of suitable electrically insulating material which arbor is provided with a keyway or aperture 96 adapted to receive pin 98 which passes through the keyway 96 and through the similar keyway or aperture 100 in the end of shaft 12 with a friction fit to secure the arbor 94 on the end of the shaft. Arbor 94 is bifurcated or slotted at its upper end in FIGURE 2 as illustrated at 102 and secured in this slot by a screw or other suitable fastening device is an electrically conductive spring metal shorting clip 104 having spaced upper and lower resilient spring arms 106 and 108 as more clearly illustrated in FIGURE 4. Spring arms 106 and 108 are adapted to wipe over the upper and lower surfaces, respectively, of wafer 1'5 adjacent its inner edge so as to sequentially engage the delay contacts D D etc., common lead 72, and zero setting contact 22. The upper spring arm 106 sequentially engages the delay contacts and the zero setting contact whereas the lower spring arm 108 continuously engages common lead or contact 72 during the entire 360 rotation of shaft 12 and arbor 94.

Long delay clock 84 in addition to top plate 82 includes a pair of further spaced parallel plates 110 and 112 on which is mounted a conventional spring driven timing clock works including escape wheel 114. This escape wheel forms part of a Junghans fuze escapement, more fully shown in FIGURES 5 and 6 and more completely described below. The escape wheel is provided with a plurality of apertures 116, any one of which is adapted to receive the up-turned semi-circular end 118 of a. detent spring or starting lever 120. The other end of this flexible and resilient metallic spring lever 120 is attached to the lower plate 112 as illustrated in FIGURE 2 at 122.

The lower end of the timing assembly terminates in a base plate 124 to which is secured one end of a pair of coiled compression springs 126 and 128. These springs are wrapped around pins 130 and 132 pressed into plate 124 at 136 and 138. Seismic set back mass 134 is suitably drilled so as to slide freely over pins 130 and 132. The other end of springs 126 and 128 support the seismic set back mass 134. In this way springs 126 and 128 bias setback mass 134 upwardly to its uppermost position but are adapted to be compressed when an acceleration force is applied to the setback mass 134 in the direction of arrow 140 in FIGURE 2. When the acceleration force is applied, setback mass 134 moves downwardly, sliding over and guided by pins 130 and 132 and compressing springs 126 and 128.

The upper end of the setback mass 134 is slotted as at 142 so that in its uppermost position it passes over arbor '144 on which is rotatably mounted an eccentric mass 146 and the edges of the slot 142 engage a pin 148 carried by the eccentric mass 146. When the timer is at rest and in the locked position pin 148 is in vertical alignment with the arbor 144 so that both are received in the slot 142. The eccentric inertial mass 146 is provided with a cam surface 150 which is engaged by one end of a cam follower pin 158 slidably received through a suitable bushing 152 friction fitted in plate 112.

The other end of the follower pin 158 engages the underside of resilient starting lever 120. This lever normally resiliently biases the pin into engagement with cam surface 150 before the unit is started. However, when the device is subjected to a force of acceleration in the direction of the arrow 140, mass 146 rotates in a clockwise direction, bringing an aperture 156 in cam surface 150 into alignment with the lower end of follower pin 158 such that the end of pin 158 falls into the aperture or hole 156. This permits the pin to move downwardly under the bias of the starting lever 120 and in so doing the upturned end 118 of the lever is withdrawn from aperture 116 of escape wheel 114. By design, escape wheel 114 is inherently self starting. Therefore, upon release of escape wheel 114, long delay clock 84 starts to run.

Provided on the back side of the inertial eccentric mass 146 are a pair of additional pins 160 and 162 which are received with a friction fit through apertures 164 and 166 of a sector gear 168 such that the sector gear is carried for limited rotational movement with the mass 146, i.e., the sector gear rotates with the mass 146 from the position illustrated in FIGURE 2 to the position assumed by the mass when the end of follower pin 158 falls into the hole 156. Annular sector gear 168 carries .teeth 170 engaged with the teeth of the first gear of a gear train 172 terminating in a verge (or clutter) escapement that controls the rotation of eccentric mass 146.

In operation of the timing unit 60 of FIGURE 2, either at the factory or in the field, the zero indicator 48 and its battery 50 are first coupled to the switch 10. The mainspring (not shown) of long delay clock 84 is then completely wound and the clock manually started and run to drive shorting clip 104 until the resilient spring finger 106 engages zero setting contact 26 of wafer 15. At this time the spring fingers complete a circuit to the zero indicator or light bulb 48 by way of leads 62 and 64 and a visible indication of the position of output shaft 12 and of the switch is given. At this time the operator then manually stops the long delay clock 84. The clock is in this way accurately zeroed in a position wherein the shorting clip 104 isengaging the contact 26 and the delay provided by clock 84 is dependent only upon the accuracy of the clock since the distance through which the output shaft must rotate, i.e., the distance from contact 26 to delay contact D (or any of the other delay contacts previously wired in) is accurately determined.

After the long delay clock 84 has been stopped, mass 146 is rotated to the position illustrated in FIGURE 2 such that the end 118 of the starting lever 120 moves into the closest one of the apertures 116 of escape wheel 114.

The bias of the starting lever holds pin 158 in the correct position. During rotation of the mass 146, set back mass 134 is manually depressed but when the arbor 144 (mounted on a suitable support which is not shown) and pin 148 are brought into vertical alignment set back mass 134 is released so that slot 142 engages pin 148 thus locking the entire assembly in the proper position.

Before insertion into the rocket the Zero indicator 48 and its battery 50 are uncoupled and removed from the unit. At lift-off the set back mass 134 is moved down- 'wardly against springs 126 and 128 by the forces of acceleration which must be of sufiicient magnitude to cause the set back mass 134 to move downwardly far enough to release pin 148. These same acceleration forces cause eccentric inertial mass 146 to rotate in a clockwise direction, the rotation of this mass being governed by the clutter gear escapement 172. After a relatively short time, i.e., a fraction of a second as determined by the clutter escape ment, pin 158 falls into the hole 156 releasing escape wheel 114, causing the long delay clock 84 to start up, Operation of the clock 84 drives output shaft 12 in turn moving shorting clip 104 from zero contact 26 over the delay contacts until it reaches delay contact D At this time the circuit is completed from energy cell 40 through common lead 70, common contact 72, the conductive shorting clip 104, delay contact D and output lead 66 to the igniter load 32. The return from the load to the other side of the battery is by way of lead 68. Thus the total time between the initiation of sufircient inertial forces to actuate the device and the activation of load 32 is governed almost exclusively by the running time of the long delay clock 84.

FIGURES 5 and 6 show an arrangement for even more accurately providing a correct zero setting for the long delay clock 84 of FIGURE 2. In FIGURES 5 and 6 like parts bear like reference numerals. As illustrated in FIG- URE 5, wafer 15 is detachably coupled by way of leads 176 and 178 through power supply battery 50 to the input terminals of a rotary solenoid 180. The solenoid is provided with a rotary output shaft 182 on 'which is mounted a lever arm 184 carrying a thin, flexible and resilient metallic strip 186. This strip is provided to stop the running of the long delay 'clock 84 when the solenoid is energized.

As previously mentioned, the clock 84 is provided with a Junghans fuze escapement including the usual pallet 188 rotatably mounted at 190 which pallet carries small weights 192 and 194 at each end. Carried by the pallet are the usual pallet pins or jewels 196 and 198 adapted to alternately engage the successive teeth 200 of the escaped wheel 114. In the Junghans escapement the jewels 196 and 198 are conventionally made of metal rather than of ruby or other jewel material. The escapement is also provided with the usual elongated balance spring, a portion of which is illustrated at 202 in FIG- URE 6, engaging the spaced banking pins 204 and 206. It is understood that the balance spring or hair spring 202 is connected to the pallet 188 in the usual manner and is provided with a secondportion extending to the other side of the pallet and engagable 'with a second pair of banking pins (not shown). Balance spring 202 sustains oscillations of the pallet between the full line position illustrated in FIGURE 6 where jewel 196 engages a tooth 200 to the dotted line position illustrated where jewel 198 engages the next tooth 200 of the escape wheel 114. The escape wheel is urged or biased for rotation in the conventional manner by a suitable main spring (not shown).

In FIGURE 5, the starting lever 120 is shown moved downwardly clear of the escape wheel 114 by its own bias and the long delay clockwork 84 is started so as to drive the spring clip 104 with the mainspring of the delay clock fully wound or substantially so. When shorting clip 104 engages zero contact or segment 26 on the wafer 15 the circuit is completed from power supply 50 to the rotary solenoid 180. Upon energization the output shaft of the solenoid rotates moving resilient detent strip 186 from the dash line position in FIGURE 6 to the solid line position illustrated in that figure. In so doing strip 186 engages the pallet 188 moving the arm of the pallet carrying weight 192 radially inwardly toward the escape wheel causing jewel 196 to engage and lock against a tooth 200 of the escape wheel, thus automatically stopping the escape Wheel and hence the running of the long delay clock 84. Once the long delay clock has been stopped by the solenoid with the shorting clip 104 engaging zero setting contact 26, turned over end 118 of starting lever 120 is inserted in one of the apertures 116 in the escape Wheel and mass 146 is locked in the correct position in the manner previously described. The unit is ready for operation and the stopping circuit including the power supply 50 and rotary solenoid 180 are uncoupled and removed from the unit.

It is apparent from the above that the present invention provides a novel timing device particularly suited for use in aerospace applications which provides a very accurate long time delay. While described in conjunction with the ignition of a rocket motor it is apparent that the switch and timing mechanism of the present invention has general utility in suitations where it is desired to provide an accurate, relatively long delay, i.e., in the order of ten to thirty seconds and more.

In one embodiment constructed in accordance with the present invention, the unit incorporated as a source of output energy to be released by closure of the selected set of contacts an energy cell 40 in the form of an Eveready type E93 alkaline cell. The cell was friction fitted in a metallic case and is rated to deliver 6 amperes flash current at 1% volts positive, at zero degrees centigrade. Higher outputs are available at higher temperatures. In this embodiment time delays from ten to thirty seconds are selectible depending on which one of the delay terminals is Wired to the load 32. The delay begins when the device is subjected to an axial acceleration of gs or greater and of suificient duration to permit the safety and arming device, i.e., the setback mass and short delay timer clutter 172 to operate. After this arming delay dependent upon the value and time of acceleration the safety and arming device unlocks the long delay clock 84. The output shaft of the long delay clock makes one complete revolution in about 35 seconds, driving the rotor 14 as it rotates.

The total time delay is the sum of the arming delay and the long delay timer. The arming delay is conventionally on the order of a fraction of a second, typically arming delays (i.e. calibrations) being furnished for minimum accelerations of 5, 10, 15, and g's. The accuracy of the long delay timer depends both on making the proper connection to the correct output delay terminal and also properly zeroing the clock. The zeroing can be readily performed in an efficient manner by a skilled technician, and may be accomplished using a simple continuity tester to an accuracy of /2 second. If the factory type setting system such as that illustrated in FIGURES 5 and 6 is used the zero setting error can be reduced by a factor of 10 or more.

In the embodiment described the entire device complete with battery carrier is less than 5% inches long. It mounts in a 1% inch bore. Mounting is by set screws threaded radially through the inch wall of the mounting tube and seating radially in a central plate of the timer. The unit may be prepared for shipment by being assembled complete, finally wound, the long delay clock zeroed, and the Whole device including battery sleeve sealed in a plastic envelope and commercially packed. The components are secured to each other by suitable threaded fasteners, pins and eyelets to make a rigid general assembly except for the battery case which is normally friction fitted to permit readily access for installing the energy cell. The battery cell may be secured to the next component if desired (or it can be screwed to its base) by a bayonet lock, or similar attachment. This serial construction (as best seen in FIGURE 2) along the axial line of the missile insures that the direction of the flight is such as to assist rather than to buck the detenting system used to arm the long delay clock.

Important features of the present invention include the zeroing segment or contact on the switch 10 which makes it possible to zero the device accurately by running it until a circuit is made across the common and zeroing contacts and then stopping the escapement of the long delay clock. The accuracy of zero setting is a function of the sophistication of the stopping system. For best results, as described, this is an electromechanical system utilizing a solenoid to stop the escapement. Such a system repeats within a very few, approximately 5, milliseconds. Manual field resetting can be accomplished by a technician using a continuity checker to within one-half second. Accuracy of the Junghans fuze escapement is on the order of 0.1%.

In addition to the increased accuracy provided, the setting and zeroing system described completely eliminates the necessity for clutches, brakes, and the other more complicated and hence expensive mechanical devices previously used. As compared to the pyrotechnic igniters for rockets having an accuracy of approximately i20% the delay unit of the present invention provides a timing delay having accuracies of i2% or better. This represents at least an order of magnitude improvement over present practice.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. A sequential timing switch comprising a spring driven clockwork having an escapement controlled rotatable output shaft, an electrically conductive wiper arm carried by said output shaft for timed rotation with said shaft, a plurality of delay contacts angularly spaced adjacent the path of movement of said wiper arm whereby said wiper arm sequentially engages said delay contacts, said delay contacts including a zero contact, a common contact continuously coupled to said wiper arm, and means connected to said zero and common contacts for coupling an electrical indicator between said zero contact and said common contact.

2. A switch according to claim 1 wherein said coupling means comprises a pair of electrical terminals, and a quick disconnect coupling for electrically connecting an electrical indicator to said terminals.

3. A switch according to claim 1 including an electrical indicator and power supply coupled in series between zero contact and said common contact.

4. A switch according to claim 3 wherein said indicator comprises an electric light.

5. A sequential timing switch comprising a spring driven clockwork having an escapement controlled rotatable output shaft, a stationary annular wafer of insulating material having spaced, fiat opposite sides positioned adjacent said output shaft, a plurality of planar delay contacts angularly spaced along its radial inner edge on one side of said wafer, said delay contacts including a zero contact, an annular common planar contact on the other side of said wafer adjacent said inner edge, a shorting clip rotatably mounted within said wafer on said output shaft, said clip being insulated from said shaft, said shorting clip having spaced arms resiliently engaging said sides of said wafer while said arms wipe over said contacts, a contact terminal on said wafer for each of said contacts, means connected to said common and zero contact terminals for coupling an electrical indicator between said common contact terminal and said zero contact terminal, and means for coupling at least one of said delay contact terminals other than said zero contact terminal to an output load.

6. A switch according to claim including means coupled to said clockwork for stopping said clockwork.

7. A switch according to claim 5 including a load and first power supply coupled in series between said common contact terminal and said other contact terminal, and an indicator and second power supply coupled in series between said zero contact terminal and said common contact terminal.

8. A switch according to claim 5 including means coupled to said spring driven clockwork for braking rotation of said output shaft, and a second escapement controlled timing movement including an unbalanced mass coupled to said braking means for releasing said braking means in response to acceleration forces acting on said mass.

9. A delay device comprising a spring driven clockwork having a rotatable output shaft, an electrically conductive wiper arm carried by said output shaft, a plurality of delay contacts angularly spaced adjacent the path of movement of said wiper arm whereby said wiper arm sequentially engages said delay contacts, said delay contacts including a zero contact, a common contact continuously coupled to said wiper arm, means for coupling an electrical indicator between said zero contact and said common contact, an electrical indicator and power supply coupled in series between said zero contact and said common contact, said indicator comprising a solenoid having a movable armature, and means coupled to said armature for stopping said clockwork upon movement of said armature.

10. A delay device comprising a spring driven clockwork having a rotatable output shaft, a stationary annular wafer of insulating material having spaced, flat, opposite sides positioned adjacent said output shaft, a plurality of planar delay contacts angularly spaced along its radial inner edge on one side of said wafer, said delay contacts including a zero contact, an annular common planar contact on the other side of said wafer adjacent said inner edge, a shorting clip rotatably mounted within said wafer on said output shaft, said clip being insulated from said shaft, said shorting clip having spaced arms resiliently engaging said sides of said wafer whereby said arms wipe over said contacts, a contact terminal on said wafer for each of said contacts, means for coupling at least one of said delay contact terminals other than said zero contact terminal to an output load, means for stopping said clockwork, said clockwork including an escape wheel and resilient force responsive means coupled to said escape wheel for locking said clockwork against operation.

11. A timer comprising a selector switch having a plurality of output terminals and a zero terminal, a power supply, a load coupled to one of said output terminals, a spring driven clockwork for sequentially coupling said power supply to each of said output terminals, movable force responsive means coupled to said clockwork for braking said clockwork, and means for coupling an indicator circuit to said zero terminal for indicating the zero position of said selector switch, said force responsive means including a seismic mass working against a verge escapement.

12. An ignition timer comprising a selector switch having a plurality of output contacts, means for coupling an ignition load to one of said output contacts, a rotor having a wiper arm sequentially engageable with each of said output contacts, a spring operated long delay clock operably connected to said rotor, a power supply having one side coupled to said load, and its other side to said wiper arm, braking means coupled to said long delay clock, a force responsive short delay clock coupled to said long delay clock for releasing said braking means, said short delay clock comprising an unbalanced mass mounted for movement against the retarding force of a clutter escapement, and set-back mass means coupled to said unbalanced mass, for locking said unbalanced mass against movement for acceleration forces of less than a predetermined amount.

References Cited UNITED STATES PATENTS 2,794,081 5/1957 Luhn 200166 X 2,834,851 5/1958 Mastney et al 335-138 X 3,089,923 5/196-3 Wright 20011 2,900,913 8/ 1959 Sheeley 102-84 2,958,282 11/ 1960 Czajkowski 200*-37 X 3,061,693 10/ 1962 Reihman 20037 3,088,408 5/1963 Richardson 10284 3,129,666 4/ 1964 Nabreski 102-84 3,239,740 3/1966 Locke 200-167 X BERNARD A. GILHEANY, Primary Examiner.

F. E. BELL, Assistant Examiner. 

